Magnum Spring Gun Design Numbers or Principles Wanted.
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Magnum Spring Gun Design Numbers or Principles Wanted.
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Topic: Magnum Spring Gun Design Numbers or Principles Wanted. (Read 3630 times))
I_like_Irons
Shooter
Posts: 97
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Real Name: David Read
Magnum Spring Gun Design Numbers or Principles Wanted.
«
on:
February 16, 2016, 12:28:22 PM »
What I want:
Minimum barrel length for a magnum springer producing about 850 ft/s with fairly heavy pellets, 1.3 to 1.4 times round ball weight. This should be in terms of caliber, but I can do the conversions if you list barrel length and caliber. (example: a .177 pellet that weighs 10.5 to 11.2 grains)
Swept volume required (in terms of barrel volume, or energy is good).
Ideal compression chamber geometry. For example is a "soup can" shape ideal, or is a longer smaller diameter or a larger diameter shorter stroke better?) (Note: The "soup can" shape minimizes surface area for a given volume. )
Hammer mass required (in terms of pellet mass, or energy, or . . . .)
The spring energy, I already can figure out along with stroke length
What I intend to use this information for: Design a spring powered Howitzer-Gun lobbing a one pound pellet at 800 to 850 ft/s. Whether it ever gets built remains to be seen, but for right now designing one is of interest. Initial bore diameter thoughts are going to be around 1.5".
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rsterne
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Bob and Lloyd
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Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #1 on:
February 16, 2016, 06:48:52 PM »
This thread may help you with question #2....
http://www.gatewaytoairguns.org/GTA/index.php?topic=94485.
From the data I presented in that thread, 3cc's of swept volume per FPE seems a good design point.... Since you are talking about 10,000 FPE of muzzle energy (or more), and assuming you can scale up current springer technology to that size, you would be looking at a swept volume of about 30,000 cc (30 litres), which would be 1830 CI, or just over 1 cubic foot....
If you read further in that thread, you will find that the typical bore/stroke ratio for Springers is about 3 or 4 to 1.... Using 3:1, and 1830 CI, you would have a bore of 9.2" and a stroke of 27.6".... If the stroke was 4 times the bore, you would have an 8.3" bore x 33.4" stroke.... If the ratios hold true, and you want to drive your 1 lb. pellet at 850 fps (11,233 FPE), you might want to use a 9" bore and 32" stroke as a design point for the compression cylinder....
I regret I have no information about the optimum barrel length, piston mass, or the spring you may require.... but suggest that perhaps something along the lines of a suspension spring from a truck might be in the ballpark, and should fit inside a 9" cylinder.... You may have to stack several of them on top of each other to achieve a 32" stroke without achieving coil bind, however....
HTHs....
Bob
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1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
Airgun.Sniper
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Posts: 3392
Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #2 on:
February 16, 2016, 07:52:36 PM »
Way over my pay grade for sure....but IM learning its a slow process but I am
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Benjamin Maruader Gen II .22 cal LW Barrel
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grimeszee
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Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #3 on:
February 16, 2016, 08:07:31 PM »
That's what I was going to say Bob.
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I_like_Irons
Shooter
Posts: 97
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Real Name: David Read
Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #4 on:
February 16, 2016, 09:31:14 PM »
Bob,
The original idea was a product of looking at some various steel tubing in the shop I used to work, and truck suspension springs that one of the other guys was swapping out of his truck. It's been sitting in the back of my head for sometime now.
However, for this thing I will probably go with an air piston spring instead of steel coil springs. The size of your estimated piston/cylinder seems to scale nicely with what I envision. The primary advantage with the air spring, is that I can adjust pressure to change the power, and make it large enough so that the force is fairly uniform. That coupled with an adjustable top hat, will make for a tunable artillery piece.
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rsterne
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Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #5 on:
February 16, 2016, 10:37:02 PM »
You're actually serious, and not at all put off by what I wrote then....
.... I tried very hard to keep a straight face as I worked through the numbers....
Most Springers seem to need a barrel length of about a foot, which is 54-67 calibers.... If we use 60 calibers long (a 16" Naval Gun is 50 calibres long), we would get 10.6" in .177 cal, 13" in .22 cal, 15" in .25 cal.... and 90" in 1.5" calibre.... That sounds workable, don't you think?.... I guess just to be sure it was long enough you could start with 8 feet.... That's what I would do....
if I was crazy
....
I'll leave you to figure out the spring yourself....
Bob
«
Last Edit: February 17, 2016, 12:39:55 AM by rsterne
»
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Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
I_like_Irons
Shooter
Posts: 97
yes
Real Name: David Read
Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #6 on:
February 16, 2016, 11:11:06 PM »
Bob,
The more I work through the numbers, the more it looks like it is just a mere matter of scale. Say for a given .22 going up to a .44, you only have to double all the dimensions. The mass or weight of stuff will go up proportionally as well, along with energy (by the cube). This implies to me that the ideal mass of the piston is also just a proportion to the mass of the pellet. The only factor that does not scale as one would like is the spring force. It goes up by the square. However, if you lengthen the cocking arm proportionally, then the cocking force also goes up as expected.
I'm glad you know about the convention of expressing gun barrel lengths in terms of calibers. This really makes the most sense to me. I was kind of wondering if this thing wouldn't be best as a 1.5 - 38 or 50 as well. It would appear that the Air-Arms TX200 only has a nine inch barrel and is, therefore, in this ballpark.
And, yes I am serious about designing the thing. Actually getting around to building it is another matter entirely.
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rsterne
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Bob and Lloyd
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Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #7 on:
February 17, 2016, 12:49:58 AM »
I personally would not go less than 50, I think 60 would be a better place to start, it's not ridiculously long at 90" (I originally said 75" above)....
I would work out the spring force by estimating the pressure you need.... you know the area of the piston, so figure back to get the force.... Once again, there is some information in that thread to work from.... About half way down the second page I talk about "piston pressures" of 171 psi (cocked) and 132 psi (uncocked) as numbers that worked in a Phantom.... If you had a 9" piston, that is 64 sq.in., so to achieve those pressures with a gas ram, you would need one with a force of....
171 x 64 = 11,000 lbs, cocked and 132 x 64 = 8,500 lbs. uncocked.... with a stroke of 32".... Note this is NOT the air pressure at the end of the firing stroke, it is how hard the spring / gas ram is pushing on the piston....
You can double check the numbers by taking the average force (11,000 + 8,500) / 2 = 9,750 lbs. x (32 / 12) = 9,750 lbs. x 2.67 ft. = 26,000 FPE.... Figure a 50% loss, and you're right about there....
Bob
«
Last Edit: February 17, 2016, 12:55:05 AM by rsterne
»
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Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
Back_Roads
I Got A 15 Pump BB Gun :) BB Guns Got Much More Complicated :)
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1st Edition Crosman 760 Pump Master
Real Name: James Seiler
Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #8 on:
February 17, 2016, 12:57:31 AM »
Dang I just had the brief idea like @ 3 am CT this am. ,of using a gas car strut and some other insane ideas ,, are springer cannons in our future
<hears twilight zone music>
BTW i had one as a kid
«
Last Edit: February 17, 2016, 12:59:08 AM by Back_Roads
»
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Scotchmo
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Real Name: Scott Hull
Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #9 on:
February 17, 2016, 01:32:02 AM »
Just the wire spring for this gun would probably weigh about 1000lbs.
Go with a gas spring.
Better yet, a dump chamber. The pump mechanism to recharge would be simpler than trying to cock that monster spring.
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rsterne
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Bob and Lloyd
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Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #10 on:
February 17, 2016, 01:42:01 AM »
I'm not sure if Lloyd's PCP calculator will actually DO this calculation without running out of lines for the integration.... but it says 3500 psi in a 30,000 cc reservoir and a 48" barrel should give you 816 fps with a 7000 gr. pellet in 1.5" caliber at 60% efficiency....
Bob
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Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
I_like_Irons
Shooter
Posts: 97
yes
Real Name: David Read
Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #11 on:
February 17, 2016, 10:44:34 AM »
The PCP version of this thing would start with a 6K nitrogen bottle. The bottles would be swappable.
Oh, I have no illusions that this will have to be towed to the range. It will have its own carriage. It is a howitzer after all.
I'll start another thread once I start on some drawings.
Oh, and for the spring energy, I thought I'd use the standard efficiencies of spring guns which is between 0.3 and 0.4. So, for the design I'll need somewhere in the neighborhood of 32,000 ft-lbs. For a 3 ft stroke, it would only take an average spring force of 10,700 pounds or so. (Roughly five to six tons). For a gas spring piston area of say 50 square inches, it will only take slightly over 200 psi to achieve this.
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rsterne
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Bob and Lloyd
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Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #12 on:
February 17, 2016, 01:28:11 PM »
However, to get an AVERAGE pressure of 200 psi on your 50 sq.in. piston with a 3 foot stroke, you would need a 4.5 foot long cylinder (or an auxiliary chamber), starting at 100 psi uncompressed and ending at 300 psi compressed.... or some other similar ratio.... Of course you could use a setup like a gas ram where the diameter of the piston rod is the only part seeing a difference in pressure, running inside a much larger cylinder.... but then you need either a larger cylinder or much higher pressure....
Bob
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Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
rsterne
Member 2000+fps Club
Bob and Lloyd
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Posts: 26958
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Real Name: Bob
Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #13 on:
October 27, 2017, 03:03:19 PM »
I realize this thread is well over a year old.... but a recent discussion about cocking a springer with HPA made me come back to post this thought.... If you had my suggested 9" compression chamber, with a 32" stroke.... and required a force of about 11,000 lbs. to cock it.... you could use compressed air in front of the piston to compress the gas ram behind it.... That 9" piston is 64 sq.in., so if you had 200 psi air that gives you 12,800 lbs. of available cocking force.... Now you would need a pretty large tank to supply the 1.2 CF of 200 psi air each time you cocked it (without the pressure dropping below 200 psi).... but it could be done.... Just one more piece of the puzzle....
Bob
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Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
Back_Roads
I Got A 15 Pump BB Gun :) BB Guns Got Much More Complicated :)
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Posts: 15930
1st Edition Crosman 760 Pump Master
Real Name: James Seiler
Re: Magnum Spring Gun Design Numbers or Principles Wanted.
«
Reply #14 on:
October 28, 2017, 08:12:59 PM »
Hmm or a pumper to supply the cocking force
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Magnum Spring Gun Design Numbers or Principles Wanted.